This invention relates to a device for cleaning the outer circumferential surface of rotary cylinders or rollers used in printing machines or in other types of machine such as paper and/or film production and processing machines, on which deposits of various materials, such as ink, form and have to be removed for proper machine operation.
The state of the art comprises cleaning devices provided with two shafts for unwinding and rewinding a fabric which is made to adhere to the rotary cylinder or roller by means of a presser member, which can be in the form of an air chamber or a blade of flexible metal or resilient material.
Because of their characteristics and method of operation, these conventional devices have drawbacks in use, and do not ensure either adequate cleaning or optimum fabric and detergent consumption. Specifically, in the case of devices comprising an air chamber, this performs two functions, namely those of bringing the fabric into contact with the cylinder and of pressing it against the cylinder. The air is fed into the air chamber and then discharged several times during each cleaning cycle, to the detriment of the elasticity of the chamber, which undergoes variation both because of pressure reduction and leakages, with immediate negative effects on operation, and because of continuing decay in the characteristics of the rubber from which the chamber is constructed. Excessive chamber air pressure or wear involve the risk of chamber bursting with consequent danger to the operator. To this can be added the traction effect exerted by the rotary cylinder on the chamber via the fabric, causing chamber deformation which cannot always be compensated by the pressure exerted by it in the contact region. In the particular case of cylinders which do not have a continuous outer circumferential surface but instead comprise, as for example in the case of blanket cylinders, a gap in the direction of the generating line, this deformation is even more evident, resulting in vibration on passing said gap during rotation, this vibration adversely affecting the quality of the contact offered by the air chamber.
In the case of cleaning devices provided with a contact blade, the pressure exerted on the cylinder via the fabric is not always uniform along the entire cylinder length, and any irregularities in its surface or even minimum misalignment between the blade and the cylinder axis prevent its proper cleaning. In the case of the aforesaid discontinuous cylinders the said vibration problem also exists, in that the blade is unable to maintain the fabric in contact with the cylinder surface, not because of deformation but because of its limited flexibility and elasticity.
In an attempt to at least partly solve the said problems, it is usual to increase the cleaning time even though this results in greater fabric and detergent consumption.
The main object of the invention is to provide a cleaning device which is quick and simple in use and results in proper and efficient cylinder or roller cleaning and an appreciable saving in fabric and detergent.
This and other objects which will be more apparent from the ensuing detailed description are attained by a cleaning device in accordance with the accompanying claims.